Nonreciprocal Magnetic Coupling Using Nonlinear Meta-Atoms.
Nonreciprocal Magnetic Coupling Using Nonlinear Meta-Atoms.
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DOI：
10.1002/advs.202001443
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发表时间：
2020-10
期刊：
影响因子：
--
通讯作者：
Zhang X
中科院分区：
文献类型：
--
作者：
Zhao X;Wu K;Chen C;Bifano TG;Anderson SW;Zhang X
打破洛伦兹互易性是功能射频（RF）和光学器件阵列的基础，如隔离器和环行器。外部激励的应用，如磁场和时空调制，已被用来实现非互易响应。或者，也可以采用非线性效应来以完全被动的方式打破互易性。在此，提出了一种由线性和非线性Meta原子组成的耦合系统，该系统基于其组成Meta原子的耦合和频率失谐来实现非互易性。基于耦合模理论（CMT），建立了一个分析模型，以设计和优化该耦合系统中的非互易Meta原子。进行了射频隔离器的实验演示，前向和后向传播之间的对比度约为20 dB。重要的是，本文开发的CMT模型的使用使预测基于非线性的非互易性的限制的可推广能力成为可能，从而促进了打破洛伦兹互易性的新方法的开发。CMT模型和实施方案在这项工作中提出的可以部署在广泛的应用，包括集成光子电路，光学超材料，超颖表面，等等。打破洛仑兹互易性是一系列功能电磁器件的基础，通常需要外部激励。磁耦合的线性和非线性Meta原子在实验上被用来实现巨大的和可控的非互易性。这种无源和无磁体的非互易隔离器的物理探索通过使用耦合模理论所提出的方法的推广。
Breaking Lorentz reciprocity is fundamental to an array of functional radiofrequency (RF) and optical devices, such as isolators and circulators. The application of external excitation, such as magnetic fields and spatial–temporal modulation, has been employed to achieve nonreciprocal responses. Alternatively, nonlinear effects may also be employed to break reciprocity in a completely passive fashion. Herein, a coupled system comprised of linear and nonlinear meta‐atoms that achieves nonreciprocity based on the coupling and frequency detuning of its constituent meta‐atoms is presented. An analytical model is developed based on the coupled mode theory (CMT) in order to design and optimize the nonreciprocal meta‐atoms in this coupled system. Experimental demonstration of an RF isolator is performed, and the contrast between forward and backward propagation approximates 20 dB. Importantly, the use of the CMT model developed herein enables a generalizable capacity to predict the limitations of nonlinearity‐based nonreciprocity, thereby facilitating the development of novel approaches to breaking Lorentz reciprocity. The CMT model and implementation scheme presented in this work may be deployed in a wide range of applications, including integrated photonic circuits, optical metamaterials, and metasurfaces, among others. Breaking Lorentz reciprocity is the foundation of an array of functional electromagnetic devices, and often requires external excitation. Magnetically coupled linear and nonlinear meta‐atoms are experimentally employed to achieve giant and controllable nonreciprocity. The physics of such a passive and magnet‐free nonreciprocal isolator are explored by using coupled mode theory for generalization of the presented approach.
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